13 September 2007

2 comments:

Best features of the central business district power grid are built-in redundancy, and underground distribution.

Hidden wires don't obscure the beautiful architecture of our buildings. They’re safer than overhead lines because they can't blow down in a storm. Being encased in concrete under the sidewalk makes them more reliable because it's hard to accidentally cut them, or for Al Qaeda to blow them up.

We call it a “grid” because wires criss-cross all of downtown just like the streets. It’s redundant because the power company (CG&E, Cinergy, Duke, or whatever they’re called these days) feeds the grid from opposite ends using two totally independent power sources. This means we can lose any one of the feeds, any one of the sub-stations, or any two distribution legs, and ALL the end users will still have adequate power.

This turns out to be a very valuable public utility to have downtown. A high-rise is a building over 75 feet tall. That's the limit of fire truck ladders. Higher than that, and the building itself becomes part of the rescue apparatus. Special rules require sprinklers, fire & smoke proof stair shafts, alarms & PA sytems, and elevators that remain operational for the firemen. To do this they need a backup power source so all this electrical stuff runs no matter what. Ordinarily the backup source is a combustion engine generator. But in our downtown, it’s inherent in the grid.

Dozens of tall buildings have avoided purchasing costly gensets and have avoided the pollutants that are produced by testing them every 30 days. This benefits their shorter neighbors, too.

What I find most impressive is that the cost of this system versus one with no redundancy is negligible. Downtown uses enough power that it would have required two sources anyway. The wiring grid had to be installed anyway, but redundancy just made the wires one or two sizes bigger. Tying two sources together using the gird literally costs nothing.

A little bit of forethought by some bright people provided a system that is way more than the sum of its parts. Those old farts who gave us this city really had their act together.